1. Technical Field of the Invention
The present invention relates to safety devices for press brakes. More particularly, the present invention relates to a safety device for a press brake, wherein the safety device is adapted to detect a foreign object within the press brake and to suspend operation of the press brake thereupon.
2. Description of the Related Art
Conventional press brakes are widely used in the prior art to bend, form or shape individual sheets of formable material, such as thin sheets of metal, into any number of useful shapes. For example, an "L"-shaped wall bracket may be formed by inserting a planar strip of sheet metal having a predetermined width, length and thickness into the press brake and manipulating the press brake in a suitable manner to bend the planar strip about an axis lying in the plane thereof and located at a predetermined location along its length.
A press brake typical of those found in the prior art includes an immobile frame having a die fixedly mounted thereto and a translatable ram having a punch fixedly secured thereto. The ram is attached to reversible driving means to permit sliding translation of the ram both in a first direction towards the frame and in a second direction away from the frame. The die and the punch are each sized, shaped and positioned relative to one another to permit the punch to be received by the die and to define the desired shape of a part formed thereby.
For example, and with reference back to the aforementioned "L"-shaped wall bracket, the press brake die may include an elongated upright "V"-shaped channel and the punch may include a cooperating upright elongated "V"-shaped downward projection, wherein the punch projection is sized to be received by the die channel. The "L"-shaped bracket is formed by an operator manually positioning the planar strip of formable material between the frame die and the ram punch, such that the planar strip lies in the path along which the ram punch travels to be received by the frame die. The ram punch contacts the planar sheet and forces it into the frame die, thereby pinching the planar strip between the ram punch and the frame die and forming the shape of the planar strip according to the engagement therebetween.
To those skilled in the art, it is known that the ram punch and the frame die oftentimes define a pinch point therebetween, thereby presenting a safety hazard to an operator thereof, who is oftentimes required to hold the planar strip in position between the ram punch and the frame die until such time as the planar strip is pinched and gripped thereby. As such, a portion of the operator's body, and more typically, the operator's hand or fingers, may be accidentally injured thereby. Various safety devices have been taught by the prior art which provide a means by which operation of the press brake is suspended in the event a foreign object, such as the operator's hand, is placed in the path along which the ram punch travels to be received by the frame die. Thus, it is desirable to provide a safety device for a press brake, wherein the risk of operator injury from the press brake is minimized thereby. It is furthermore desirable to provide a safety device for a press brake, wherein operation of the press brake is suspendable in the event a foreign object is placed therein.
For example, U.S. Pat. No. 4,166,369 to Nakajima teaches a safety device for a press brake wherein a fixed vertical curtain of light beams enclose a region of the press brake surrounding a slide portion and a lower beam portion, wherein the slide and the lower beam cooperate to define a pinch point therebetween. As the slider moves downwardly towards the lower beam, each vertically successive light beam is deactivated immediately prior to its being interrupted by the moving slider. Interruption of any of the lights beams prior to deactivation by the position of the slider, for example, when the operator places his hand in the path of the light beam, suspends movement of the slider, thereby minimizing the risk that an operator's hand may be caught in the pinch point and injured thereby. However, it is furthermore desirable to provide a safety device for use on a press brake, wherein the safety device is attachable to a moveable portion of the press brake. It is also desirable to provide a safety device for use on a press brake, wherein an operator thereof is permitted to access a region of the press brake surrounding the pinch point thereof while the ram is positioned more than a predetermined activation distance from the frame. It is even further desirable to provide a safety device for use on a press brake, wherein movement of the part being formed by the press brake does not interfere with operation thereof.